[PATCH] Calculation fix for memory holes beyong the end of physical memory

absent_pages_in_range() made the assumption that users of the
arch-independent zone-sizing API would not care about holes beyound the end
of physical memory.  This was not the case and was "fixed" in a patch
called "Account for holes that are outside the range of physical memory".
However, when given a range that started before a hole in "real" memory and
ended beyond the end of memory, it would get the result wrong.  The bug is
in mainline but a patch is below.

It has been tested successfully on a number of machines and architectures.
Additional credit to Keith Mannthey for discovering the problem, helping
identify the correct fix and confirming it Worked For Him.
Signed-off-by: NMel Gorman <mel@csn.ul.ie>
Cc: keith mannthey <kmannth@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

mm/page_alloc.c

@@ -2261,7 +2261,7 @@ unsigned long __init __absent_pages_in_range(int nid,
 
 	/* Account for ranges past physical memory on this node */
 	if (range_end_pfn > prev_end_pfn)
-		hole_pages = range_end_pfn -
+		hole_pages += range_end_pfn -
 				max(range_start_pfn, prev_end_pfn);
 
 	return hole_pages;